The GM marine 425hp 454 would be an awesome upgrade and well worth the money in my opinon. It would still get good fuel economy and probably be able to run dry with a light load too. Just my 2 cents.

 

Keith had his motor rebuilt on his 16ft boat. It is a 350 vortec and out has hells of power. Ain't shot no fish on dry ground, but yes it will run it with no problem. I wouldn't put a big block on it cause I would want to keep it as light as possible.

 

trey, i've looked at that motor and really like it but i just think its gonna be to big for the boat. Marty, i was gonna ask yall how it had turned out after he got it rebuilt. Aint real worried about running dry just moving fish down the lake, i've had close to 1200-1500 lbs in the boat and it will move it but it seems like it takes a mile to get it up

 

how much gas do you use with the small block engines?

 

I'd stay with a small block. You can get tons of power out of em and I'd want to keep it as light as possible. Save the big blocks for the 22footers.

 

yeah ive pretty much desided to stay small block, TXBA i havnt really sat down and figured it up exactly but i can feel up the 30 gallon tank and i can fish every night for a week down at the river below the house and still have way over a quarter. havnt really gotten to see how it does running wtfo for extended runs

 

You cant boost your HP much without changing props and reduction. It is all a balancing game.

 

While vortec heads make a little more power than most other factory heads, I would shy away from them. Vortec heads have more than their fair share of cracking issues. You can get a good pair of aftermarked heads that will be just as good or better than a Vortec and only cost a little more. Plus they won't have the cracking issues. I would stay away from stroking the motor to a 383. Too many horror stories involving 383's.

As mentioned above, don't forget about a possible prop upgrade with an increase in horspower.

Also, if you don't mind spending a little more money, you could go with a 6.0L. They can be had from about any junkyard and be gone through and checked out. THey are a great platform for a reliable power increase as well.

 

and what horror stories would that be?

 

I would put a iron head 425hp 454 in there, piss on HP to weight ratio, foreget fuel consumption, don't worry about having too much weight in the back of the boat....I have never owned a iron head 454 but I know dozens of people who depend on their boat to put food on the table, they swear by that motor and I have seen 16' boats with that motor in them work in swift water that likes to climb up ur transom and pull ur nose down, but they get back to the ramp at the end of every day. Get the big block.

 

What he said!

 

no replacement for displacement

 

I have a 350 sb on my boat now. I havent ran it much at all but Im going with a 454 this year. Its only 100 pounds more and thats not much when talking airboats. There are a bunch of direct drive boats out there with 350's but they dont push the weight we do. Everyone has told me to go with a big block. To me its like a troller......when you ask how big they all say go as big as you can. My boat is really 14.5 foot long but has a added 2 foot and deck. I think the 454 will be a great addition.

 

I had a 16 ft diamondaback with a 550hp 496 on a 2:1 drive with a 3 blade stump puller maxed out. The boat would go anywhere - up river banks, across dams, etc.

 

The game is who can pile the most fish in the boat. The less weight the boat has in it when you dump it off the trailor, the more weight you can put in it while your fishing. 375 - 400 hp out of a small block and that boat would rock. You will need to go to a carbon prop so you could adjust the pitch. I've come back with 542 shad in that boat and no one ever ask about the motor. 375- 400 hp should put you at about 54 degrees on a 78" paddle prop if you decide to go that route.

 

Chris, is that the airboat that vergil had for sale this time last year? I think thats his name, up in the gainsville ga area?

 

Get a big block! The iron head 454 is a great motor. Like Brady said there are people using the motors in boats that are working 6 days a week. That motor will have plenty of nuts to take you wherever you want to go, a 2.3 with a 3 blade R would make a great setup for that boat/motor.

 

whatever you go with, go with something reliable. too much "hot rod" stuff normally proves to be unreliable. the 6.0 or stock 454 with iron heads will get the job done. just have to decide what your looking for. the small block will be better on fuel but the big block will give you extra push as long as you don't have to change props to get the most out of it. some corvette heads or double bump heads may give you the little extra your looking for with the motor you have now.

 

Dude, I've made tons of power from small block V8. you do not need a big block like these guys are saying. Don't let the inferiority complex about having a small block shy you away from a small block. You could put a mild cam in that 350 and/or put the crank in it to stroke it to higher displacement and get with some Air Flow Research heads and it would make just as much power as a 454 and it would be reliable. If you change the crank, get the rotating assembly balanced. You dont need the blueprint unless you just want to have the paper and the motor will not sling apart if you add ARP bolts. if you have any questions about doing it cheap I can help with the motor....just not the blade or reduction.

 

HP isn't everything, you need the torque that comes with the Big Blocks....

The motor is under constant load when turning a prop, and a souped up small block just wont cut it.

 

My new boat is gona have a small block in it "for an anchor"

 

Sure sure you can decent power with a small block but if you put a hopped up 350 and a mild 454 making the same power right next to each other and run them the same. I'd put money on it that the 454 will last longer than the modded 350

 

Gbom, he has a mild built 350 with a ch2 2-1 reduction and a 78" 2 blade paddle prop @ 50 degrees. How much is it gonna cost this young fish killer to switch everything over to a 454?

 

how much power do you need to run 18x8 or 20x8 airboat dry land without it working hard?

 

most 18 to 20' boats are running 496 and up, somewhere in the neighborhood of 500 to 600 horsepower.

 

is the 496 chevy the same motor they put in the HD2500 and HD3500 chevy trucks like back in 2000-2002??? is that they calling the levitator? the low end torque motor just for pulling? like 8.1 Liter?

 

Do you do anything to the 454 to get more power or is it good enough stock? I can get those really cheap but since everyone was talking about high hp I have a motor ready that's why I'm asking. if you say it won't hold up I won't bother. you guys using lopey kind of cams or mild? and stock iron heads?

 

A cam with a Lope is for the drag strip and not an airboat.

Take what you know about motors and the drag strip and throw it out the window. There are some basic concepts that still apply but tons of stuff that has to be much different on and airboat engine.

 

i think I'll have to call an airboat builder to find out the specs on what they're putting in their motors to make them hold up

 

They all use crate motors. GM, Mast, Levitator, and a few others.

 

I got my information. thanks for helping.